GMROI in Retail: Formula, Benchmarks and How to Read It by Category

Margin says how much a retailer keeps on each sale. Turnover says how fast the stock sells. GMROI, gross margin return on inventory investment, puts the two together: how much gross margin each pound tied up in stock earns in a year. For a chain that buys its stock with its own cash, it is the closest single number to the return on that cash.

1. The formula

GMROI = gross margin ÷ average stock at cost, for the same period, usually a year. Gross margin is sales less the cost of the goods sold¹; average stock is the opening and closing stock at cost, divided by two, or better an average of monthly counts. A category that holds £10,000 of stock at cost on average and makes £40,000 of gross margin in a year has a GMROI of 4: each pound of stock earns four pounds of margin a year. To work out the margin on a single product from its cost and shelf price, ex VAT, use our gross margin calculator.

The same number can be read as margin times speed. GMROI equals the stock turn at cost multiplied by gross margin over cost of goods. So a category with thin margins can still earn a high GMROI if it sells fast, and a high-margin line that sits on the shelf can earn less than bread.

2. Why two GMROI figures rarely compare

Three choices change the result. The period: a figure for 28 days has to be multiplied up to a year before it reads like an annual one. The cost of sales: some retailers put warehousing, distribution or even store costs into it, which lowers gross margin. And the stock valuation: under LIFO, which many US grocers use, stock sits in the books below today's cost. Kroger's reported figures give a GMROI of 4.8; with its stock at replacement cost, which its report discloses, the same year gives 3.6².

Retailers that use GMROI set it against their own history and their own categories for that reason. Big Lots' finance chief described it as "a key metric which we're using to evaluate closeouts" when the chain decided which bought-in lines to carry³. Compare your categories and stores with each other on one definition before you compare them with anyone else.

3. GMROI by retail category

The US Census Bureau publishes, for each kind of retail business, the year's gross margin and the stock at cost at the end of each year, with cost of goods sold defined as purchases plus the change in stock, without store costs^{1, 4}. Dividing one by the other gives GMROI on a single definition across retail:

Grocery stores earn more on their stock than most of retail because food sells within days, even at modest margins. Specialty food shops, the butchers, bakers and delis, earn almost twice as much again, while a liquor store's bottles sit long enough to put it at the bottom of the chart, level with hardware stores. These are survey estimates, and the small categories move from year to year.

4. What grocers' own accounts show

The same calculation from listed grocers' latest annual reports lands in the same range, with the spread explained mostly by what each one puts into cost of sales and how it values stock^{2, 5, 6, 7, 8, 9, 10, 11}:

A chain that runs its own warehouses holds more stock per pound of sales than one supplied store by store, so its GMROI is lower for the same shelves. A smaller chain should compare itself with the shelf, not with the balance sheet of a group with distribution centres.

5. Read it by category and by store

A chain's GMROI is an average weighted by stock, so the categories and stores that hold the most stock set it, and a few slow ones can drag it down unseen. Work it out for each category in each store, over the same weeks, and look at the ones below the chain figure that hold the most capital: that is where the return on stock is lost. For a single product, the same question is answered by sell-through and days of cover.

It also moves within weeks. marql's AI category manager for Tuzeffy, the Romanian candy chain behind Yammy Way and Pralio, measures GMROI over the last 28 days and shows it as a yearly figure. On 10 November 2026 its workplace showed the chain below where it had been eight weeks earlier:

A drop means the last four weeks earned less margin for each leu of stock held. How the same chain's stock built up in unopened boxes is in the Yammy Way and Pralio success story.

6. How to raise it without emptying the shelf

There are two levers: more margin on the same stock, or less stock for the same margin. The second is usually faster, and starts with lines that hold stock without selling. A rule for delisting them should also check that the customer has something else to buy. This is the rule on the same workplace:

On 10 November 2026 it had one such proposal accepted at the Sibiu store: a bubble gum with 52 units on hand and 172 substitutes in its category, to be checked again by 14 November. The dead-stock guide covers how to find the rest.

At larger scale, Dollar General cut its consumables stock by 6% in 2025 through inventory reduction and fewer core lines, while gross profit grew; on our calculation its GMROI rose from 1.8 to 2.0¹². The company credits most of its margin gain to lower shrink and higher markups, not to the range cuts. The limit is the shelf: stock cut below what customers buy raises GMROI on paper and loses the sale, which the out-of-stocks guide shows how to catch.

7. Limitations

All GMROI values here are our own calculations from published figures, using opening and closing stock rather than monthly averages. The Census figures are survey estimates for US retail; the grocers' figures depend on what each puts into cost of sales and how it values stock. The Tuzeffy figure is one chain's 28-day reading shown per year, not an annual result.

How marql reads GMROI

marql reads sales, costs and stock for every product in every store from the POS and ERP a chain already uses. Its AI category manager answers for GMROI, measured over the last 28 days and shown per year, and proposes products to delist and to list, store by store, with shelf availability and dead stock as its guardrails. A person makes every range change.